1. Technical Field
The present invention relates to a member joining structure, and more particularly relates to a member joining structure where members are joined by a linking material.
2. Related Art
Spot-welding dissimilar materials of different nature, such as an iron-based metal plate and an aluminum alloy plate or resin material or the like, often does not yield a satisfactory bond, due to difference in the electric conductivity, thermal conductivity, melting point, and so forth, of the different materials.
Japanese Unexamined Patent Application Publication No. 2003-236673 attempts to address this issue by a dissimilar material welding method, where an aluminum alloy plate is interposed between two iron-based metal sheets, more specifically two steel sheets, to form a layered article of three layers, and the layered portion is held between a pair of electrodes of a spot welder and welded. This spot welding is performed by applying a strong electric current between upper and lower electrodes holding the layered portion by a predetermined pressure, thereby rapidly melting the aluminum alloy sheet that is the middle layer, and eliminating the molten portion of the aluminum alloy sheet from the spot welding region, thus, directly welding the steel sheets. Thus, the two steel sheets are directly spot-welded, so the bonding strength therebetween is sufficient, and further, the aluminum alloy sheet is strongly bonded to the two steel sheets.
On the other hand, in a case of attaching a member that requires deformation, such as a shock absorbing member that absorbs a shock load through deformation for example, to an automobile body member, the linkage of the shock absorbing member to the automobile body member needs to be maintained in a sure manner while allowing deformation of the shock absorbing member. There are many other structures used in joining other automobile body members as well, where linkage needs to be maintained in a sure manner while allowing deformation of the member when a load is placed thereupon.
There are cases where strongly bonding a member that has to deform restricts the deformation of the member at the bonding portion so that deformation over the entire member is inhibited, and functions according to the deformation of the member are not sufficiently manifested. For example, a shock absorbing member may have its deformability restricted at the bonding portion, such that the shock absorbing functions due to the deformation of the entire shock absorbing member may not be manifested. Moreover, strongly bonding such members may result in load stress being concentrated at the bond portion and surrounding portions when shock is applied, which may even result in rupture and other such damage.